The present invention pertains to a simplified circuit that facilitates charging or recharging of a battery for use in a short-range wireless device such as an earpiece assembly or handset.
Many portable electronic devices are configured to include a remote unit, which cooperates with a base unit. Examples include AM/FM radios, portable compact disc players, cellular telephones, and the like. The remote unit typically includes at least a speaker for broadcasting an audio signal to the user/listener, and may include a microphone for translating a voice signal from the user prior to transmission to the base unit.
While in the past it has been commonplace for these remote units to be attached to the base unit via a cord, consumers are more frequently demanding that these remote units be wireless. This is due in part to the fact that consumers do not want wires dangling from a headset or across a windshield. Manufacturers are also willing to go wireless because it eliminates a component that may be easily damaged during use. Another place the wire may get damaged is prior to storage when the user winds the wire around the remote unit to make the wire and remote unit combination as small as possible. This winding is common since few remote units include mechanisms for cord retraction.
As a result of this demand, wireless remote units are becoming increasingly common, especially in the cellular phone industry, where hands free units that communicate with the cellular phone may include a visor mounted microphone and speaker, earpiece assemblies or other headset type remote units. These wireless units typically have a transceiver, which communicates with the base unit over an RF channel. These wireless units are designed to operate at short-ranges for this communication. Short-range as used herein means less than approximately 2-3 meters. Inherently, short-range wireless communication devices must be powered by batteries, which are typically rechargeable.
In contrast to some devices, these short-range wireless communication devices are typically charged or recharged by selective mounting on the base unit, which itself may be battery powered. In such cases, a problem arises when the base unit""s power source is used to charge the battery of the remote unit. Absent a power control circuit, the remote unit continues to use power, even when recharging. Thus, there is a need to disable the wireless device during recharging so as not to drain the battery in the base unit.
The prior art provides several methods to perform this disabling function, including a manual switch, a separate connector which grounds the remote device during charging, or a logic circuit which detects recharging. All of these solutions have drawbacks. Namely, the user may forget to flip the switch; the separate connector requires additional hardware; and the logic circuit is space consumptive and expensive. Thus, there remains the need for a circuit which disables a voltage regulator in short-range wireless devices, especially a handset or earpiece.
The present invention relates to a charging circuit that overcomes some of the disadvantages of the prior art charging circuits. The circuit may be used, for example, in a headset that is charged by the battery in a wireless telephone. The circuit includes a diode, which acts as a switch to selectively change the state of the Vcontrol port of a voltage regulator in the handset. When the short-range wireless device is plugged into the charging unit, the diode is forward biased and Vcontrol is effectively grounded, or forced to state a logical LOW level. This disables the regulator, allowing the battery to charge without any unnecessary drain on the charging source from the voltage regulator. When the wireless device is unplugged, the diode becomes reverse biased, effectively acting as an open circuit, which forces the Vcontrol to a logical HIGH state, thereby enabling the regulator for normal operation. This circuit eliminates numerous elements from the circuits of the prior art and allows a simple, reliable, economical structure to be incorporated into the device to ensure proper recharging.